The IEEE 1588 Precision Time Protocol (PTP) is a standard which provides a mechanism to accurately synchronize clocks in different devices across a network, and to measure the duration of time, or residence time, a packet takes to ingress and then egress a network device. To achieve this accuracy, the IEEE 1588 standard requires hardware to measure the residence time within a device or a system. The accuracy of the residence time calculation depends on the accuracy of the packet timestamping scheme.
Conventional timestamping schemes perform timestamping in the media access control (MAC) sublayer of the data link layer. This results in inaccuracies due to latency variations in both the Physical Coding Sublayer (PCS) and the Forward Error Correction (FEC) sublayer of the physical layer (PHY) device communicating with the MAC sublayer.
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